Review Article Childhood Autism and Auditory System Abnormalities Magdalini Hitoglou, MD, PhD*, Athina Ververi, MD † , Alexandros Antoniadis, MD ‡ , and Dimitrios I. Zafeiriou, MD, PhD † Hearing disorders are common among children with autism, ranging from peripheral and sensorineural hearing deficit or loss to auditory hypersensitivity with bizarre reactions to sounds. The auditory abnor- malities and consequent sensory deprivation exacer- bate the communication deficit of autism, and early auditory assessment holds an important place in the planning of intervention and the overall prognosis of patients. Physiologic, pathologic, imaging, and neuro- chemical studies have revealed an array of aberrations in the perception and processing of the audiologic stimuli, including (among others) maturational defects, atypical lateralization, and serotonin dysfunc- tion. Ó 2010 by Elsevier Inc. All rights reserved. Hitoglou M, Ververi A, Antoniadis A, Zafeiriou DI. Child- hood autism and auditory system abnormalities. Pediatr Neurol 2010;42:309-314. Introduction Autism is a severe developmental disorder affecting pri- marily the child’s ability in the areas of communication and social interaction. Currently defined as ‘‘a syndrome pre- senting with impairment in social relatedness and commu- nication and with repetitive routines and restricted interests,’’ it is the most common of pervasive developmen- tal disorders, which also include Rett disorder, Asperger’s syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified [1,2]. The prevalence of autism has evidenced a rapid increase during the last few years, now amounting to as many as 1/ 150 children [3]. The so-called autism epidemic has been a highly controversial issue. The broadening of the diagnos- tic criteria and greater awareness among health and educa- tion professionals, as well as the occurrence of labeling biases (e.g., for reasons of funding or qualifying for supple- mentary services), are associated with the reported increase. [4]. Nevertheless, scientific interest in autism is growing, especially in terms of etiology and possible intervention. A variety of causal factors have been related to pervasive developmental disorders, including heredity, perinatal events and environmental influences, neuroanatomic changes, and neurotransmitter aberrations, among others [4]. The symptom spectrum of the disorder is rather broad, including characteristics that may appear in the majority of patients but are not included in the diagnostic criteria. Hearing disorders are common among children with au- tism, ranging from hearing deficit or loss to hearing sensiti- vity and bizarre reactions to sounds. The exact prevalence of auditory abnormalities remains unclear. In a study of 199 children with autism, Rosenhall et al. [5] reported mild to moderate hearing loss in 7.9% and pronounced to profound bilateral hearing loss or deafness in 3.5% of all cases. Gill- berg et al. [6] diagnosed hearing loss in 13.3% of an autistic group, and Jure et al. [7], in a reverse study, reported that 5.3% of a group of hearing-impaired children also presented autism. In a review of several studies, Klin [8] estimated that hearing abnormalities were present in 33-46% of all cases and reported that both sensorineural and conductive hearing disorders have been detected in patients with autism. Peripheral hearing deficits have been associated with the patients’ frequent ear infections. In a group of 162 children with autism, the reported rates of serous otitis media and re- lated conductive hearing loss were 23.5% and 18.3% re- spectively [5]. The infections have been shown to coexist with higher autistic symptomatology score, as well as with low-set ears [9]. It is noteworthy that various immune system abnormalities, including defects in different subsets From the *Unit of Communication Disabilities, 1st ENT Department; † 1st Department of Pediatrics; and ‡ 1st ENT Department, Aristotle University of Thessaloniki, Thessaloniki, Greece. Communications should be addressed to: Dr. Zafeiriou; 1st Department of Pediatrics, Aristotle University of Thessaloniki, Egnatia St. 106, Thessaloniki 54622, Greece. E-mail: jeff@med.auth.gr Received April 22, 2009; accepted October 26, 2009. Ó 2010 by Elsevier Inc. All rights reserved. doi:10.1016/j.pediatrneurol.2009.10.009  0887-8994/10/$—see front matter Hitoglou et al: Autism and Auditory Abnormalities 309